A storage subsystem provides multiple logical storage systems allocated to storage areas of multiple storage devices as being recognizable by a host computer, which enables the host computer to perform data input/output processing for the relevant logical storage systems.
If a storage subsystem receives an input/output request from the host computer, a microprocessor installed in the storage subsystem controls the data written to and read from the storage devices or performs other input/output processing, following the input/output request.
Some storage subsystems of this type include multiple microprocessors for performing input/output processing to and from storage devices. A proposed storage system including a storage subsystem of this type, for example, stores cache control information in a shared memory in advance as the control information common to all of the microprocessors, and when receiving an input/output request from the host computer, the microprocessor to perform the relevant input/output processing accesses the shared memory, reads the cache control information, determines with reference to the read cache control information whether the relevant data exists in the cache memory, and accesses the cache memory if the data exists in the cache memory, or accesses the logical storage system if the data does not exist in the cache memory (refer to Patent Document 1).    Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2008-269424